| 摘要 |
The vacuum level of a moving-band filter for dewatering and washing of gypsum is monitored and analyzed for deviations exceeding approximately /! 0.1 bar from the set-point value, to initiate remedial action by plant operators. The vacuum level of a moving-band filter for dewatering and washing of gypsum is monitored and analyzed for deviations exceeding approximately /! 0.1 bar from the set-point value, to initiate remedial action by plant operators, comprising, in the event of increasing vacuum: (a) where the slurry has formed a cake, replacing worn seals and agitation and distributor units on the filter; (b) where the slurry contains sharp-edged, fine crystals, adjusting the washer residence time via adjustments to the dissolved salt monitoring; (c) where the slurry contains a high proportion of inert fines, increasing the purge rate and flushing out of mud fines; (d) renewing the filter belt when it has reached the end of its prescribed life; and (e) where the belt-wash function is inadequate, replacing the cake stripper and overhaul the belt washing spray nozzles. Remedial action, in the event of falling vacuum, comprises: (a) with loss of cake from the belt edges and/or non-homogeneous cake thickness, replacing the worn belt guides; (b) with incorrect slurry solids content, adjusting the dissolved salt content and replacing worn hydrocyclone units; and (c) where inadequate vacuum is available at source, cleaning or replacing the vacuum pumps. The gypsum suspension is washed and thickened in a hydrocyclone battery prior to feeding the slurry to a vacuum belt filter. Generally the filtration vacuum level increases with decreasing permeability of the cake to air, and vice versa.
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